1. Field of the Invention
This invention relates to multilateral oil wells. More particularly, this invention relates to an apparatus for monitoring and controlling fluid flow within a multilateral well.
2. Prior Art
It has been known to split the flow in a multilateral well for reasons including the flow of fluids from or to the secondary bore while independently managing the primary bore. Conventional tools that split fluid flow in a single bore to a pair of parallel bores include a selective reentry tool (SRT) such as Baker Oil Tools Part No.783-55, available commercially from Baker Oil Tools, Houston, Tex. The SRT splits flow from a primary bore to two parallel bores using a Y-section. Commonly the parallel tubing string section below the set tool contains two 3xc2xdxe2x80x3 diameter bores and the string section fits well within a 9⅝xe2x80x3 standard casing. Although the device functions well for its intended purpose, the interest in controlling and monitoring flow characteristics within the multilateral wellbore is not fully satisfied by tools of the prior art such as the SRT. This is because it is difficult to determine flow rates in each of the bores independently. Prior art devices such as venturi flow meters have not been successfully used in the parallel bore section since conventionally sized 3xc2xdxe2x80x3 venturi flow meters have an outside diameter of 5.937xe2x80x3. Thus if a meter is placed next to a 3xc2xdxe2x80x3 tube, the two will not fit in the 8.5xe2x80x3 I.D. of a 9⅝xe2x80x3 casing. Because of this it has been exceedingly difficult to determine what the flow is in the individual parallel bores. Yet the desire to measure the parallel bores independently, rather than merely sensing in the single bore persists. It would be advantageous to the art to be able to monitor and control the flows in the individual parallel bores. A device which can accomplish such result is desired by the art.
The above-identified drawbacks of the prior art are overcome or alleviated by the apparatus for flow monitoring and control in multilateral wellbores.
The invention comprises a selective reentry tool of a longer length, the length being sufficient to accept a pair of venturis (or flow control devices) one in each bore of the parallel bore sub. Each flow venturi includes a port at its most restricted portion which port is accessible by an external pressure gauge (or other sensor). Moreover, preferably, a second port is provided upstream (uphole) of the venturis to measure upstream pressure ahead of each venturi. A corresponding second external gauge or sensor is also provided. The gauges or sensors are preferably mounted in recesses extending from the outer diameter surface of the sub radially inwardly. In a preferred embodiment of the invention there are two recesses 180xc2x0 apart and each located 90xc2x0 from a bore of the parallel bores. By combining the two bores and two sensor recesses this allows for the incorporation of the sensor(s) (preferably two on each side) without the penalty of the excessive outside diameter as would be the case if such a tool were constructed using prior art components. Moreover, the external sensors are protected within the recess in the sub and formerly dead space is used to house the sensors thus making better use of all resources available. It is important to note that while the foregoing statement and following discussion of an embodiment of the invention is directed to multilateral wellbore application, the device described herein is applicable to any plural tubing well. Additionally, the concept hereof provides monitoring and/or control and as such includes not only the specific example disclosed herein but also encompasses the substitution of the monitoring devices with flow control devices and the gauges/sensors with actuators. Moreover, other embodiments use combinations of flow monitoring devices/sensors and flow control devices/actuators.